S3QL is a file system that stores all its data online using storage
services like Google Storage, Amazon S3, or OpenStack. S3QL
effectively provides a hard disk of dynamic, infinite capacity that
can be accessed from any computer with internet access running
Linux, FreeBSD or OS-X.

S3QL is a standard conforming, full featured UNIX file system that is
conceptually indistinguishable from any local file system. Furthermore,
S3QL has additional features like compression, encryption, data
de-duplication, immutable trees and snapshotting which make it especially
suitable for online backup and archival.

S3QL is designed to favor simplicity and elegance over performance and
feature-creep. Care has been taken to make the source code as readable and
serviceable as possible. Solid error detection and error handling have
been included from the very first line, and S3QL comes with extensive
automated test cases for all its components.